1. Field of the Invention
The present invention relates to a method that can guarantee the Quality of Service (QoS) in a clustering topology-based wireless sensor network, and a method of allocating time slots related with this.
More particularly, the present invention relates to a method of enhancing the QoS through the formation of a more reliable path setup in the setting of a path from a source node to a destination node, and the realizing of a time slot allocation necessary for this enhancement of the QoS.
The present invention is derived from a research project supported by the Information Technology (IT) Research & Development (R&D) program of the Ministry of Information and Communication (MIC) and the Institute for Information Technology Advancement (IITA) [2005-S-106-03, Development of Sensor Tag and Sensor Node Technologies for RFID/USN].
2. Description of the Related Art
In general, data generated in a wireless sensor network includes various kinds of data, such as application data, path setup data, scheduling data containing information on time slot allocation, etc. While these kinds of data may be classified in various ways, they are typically classified into relatively low priority data, such as data periodically updated for maintenance of the network or data indicating that a node is alive, and relatively high priority data, such as an alarm message that must be rapidly and reliably delivered to a destination.
However, since all these kinds of data are mixed and delivered through one path, a technique to classify these kinds of data and deliver the classified data to destinations suitable for a specific kind of data is needed. That is, since the different kinds of data require different QoS levels, a technique that can set a transmission path suitable for data characteristics and reliably deliver the data to a destination is needed in order to support this requirement.
FIG. 1 is a schematic view showing an example of a path setup method that can be used in a wireless sensor network. Referring to FIG. 1, sensor nodes elect a cluster head on the basis of energy level through a communication with neighboring nodes to form one cluster, and the cluster head communicates with another cluster to form an upper level cluster 102. When a hierarchical structure is formed through the above procedure, it becomes possible to form one path from a source node to a destination node using this structure. In addition, all cluster headers store information on this path in a routing table, and transmit traffic to be generated later using the routing table.
FIG. 2 is a schematic view for illustrating an example of a wireless sensor network comprised of a cluster head 201 and general nodes in the cluster head 201. Referring to FIG. 2, the wireless sensor network delivers data to a destination through communication between the cluster head 201 and the general nodes 202 and through a multi-hop relay between the cluster heads 201. Since a multi-hop is generated in all nodes constituting the network, the multi-hop acts as an interference signal 203 on the neighboring nodes 202. In a conventional time slot allocation method, resources are allocated without considering the interference generated by the multi-hop.
After a path is set by transmitting and receiving routing information and if the path is cut later, the conventional communication method in a wireless sensor network cannot guarantee that data requiring a high QoS can be reliably delivered and does not take into account interference generated between the paths in the allocation of time slots after the path is set. To this end, the conventional communication method has no way of ensuring a high QoS.